I'm going to say they are mature cornish x's that have probably grown up being treated like a layer, rainging and being somewhat restricted on diet so can stand. They appear to be at least 4 months old to me since I see clear hackles there ont he roos. I'd go ahead and taste one of the roosters and see how he turns out on the table since you'll have to downsize the roos either way. And if he's tasty and not tough, probably all meaties, perhaps of the "slow" variety that sometiems grow slower.
Edit: Roos are only 12 lbs? My cornish x roos were well over 12 lbs alive when they were 8/9 weeks old. Howver... feeding regimine can make a HUGE difference on growth rate. Mine were being fed out as broilers on broiler food....